Does an association between cigarette smoking and Parkinson's Disease-related psychosis exist? Insights from a large non-demented cohort

Background: Parkinson's Disease-related Psychosis (PDP) encompasses a spectrum of symptoms ranging from "minor" hallucinations to formed hallucinations and delusions. Notably, cognitive impairment has been recognized as the strongest risk factor for PDP. Several evidences suggest a possible role of cigarette smoking in both cognition and psychotic syndromes. Objectives: To evaluate the possible independent association between cigarette smoking and PDP in a large cohort of non-demented PD patients. Methods: A cohort of non-demented PD patients was selected from the FRAGAMP study population. All participants underwent a standardised structured questionnaire to assess demographic, clinical and environmental exposure data. Clinical features were assessed using UPDRS, HY stage, AIMS, MMSE and Hamilton Rating Scale for Depression. Presence of psychotic symptoms was assessed using UPDRS-I.2 score. Diagnosis of PDP was made according to NINDS/NIMH criteria. Results: Four hundred eighty-five non-demented PD patients were enrolled [292 men (60.2%); mean age +/- SD 65.6 +/- 9.8]. Among them, 28 (5.8%) had PDP. Multivariate analysis, adjusting by HY stage, MMSE and LED, shown an independent association between PDP and "nightmares-abnormal movements during sleep" and current smoking [adjOR 7.39 (95%CI 1.45-37.69; P-value 0.016)]. Conclusions: Our findings provide interesting insights about the possible role of current smoking in facilitating the occurrence of psychotic symptoms in PD.